feat: enhance sorter simulation demo

docs/SCENARIOS.md

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+# Scenarios
+
+## normal_flow
+
+Goal: demonstrate the full cycle across B/C/D routes.
+
+Expected result: mixed B, C and D items are processed successfully.
+
+## oversized_item
+
+Goal: prove dimensions have first priority.
+
+Expected result: every item routes to C.
+
+## round_object
+
+Goal: prove roundness check after dimensions.
+
+Expected result: every item routes to D.
+
+## boundary_dimensions
+
+Goal: test min/max boundaries.
+
+Expected result: `Boundary box 450x320x320` routes to B, `Pen 9x13x148` routes to C.
+
+## close_items
+
+Goal: demonstrate queue/spacing resilience.
+
+Expected result: warning appears, queue length is shown, items are processed sequentially.
+
+## low_confidence
+
+Goal: demonstrate fallback when pseudo-CV confidence is below 0.65.
+
+Expected result: warning appears, rule-based classification still selects B or D.
+
+## jam
+
+Goal: demonstrate fail-safe behavior at stop-gate.
+
+Expected result: state becomes FAULT, conveyor speed target is 0, Reset is required.
+
+## emergency_stop
+
+Goal: demonstrate emergency stop.
+
+Expected result: state becomes EMERGENCY_STOP, conveyor speed target is 0, Reset is required.